For example, as described in Patent Document 1, there is known a film stretching machine which stretches a film in a width direction by conveying the film while gripping both side edges of the film with clips, and simultaneously increasing the distance between the clips.
In the film stretching machine disclosed in Patent Document 1, conventional clips to grip a film each have a flapper which swings so that its tip can come into contact with a placing face on which a film is to be placed and the contact angle of the flapper with respect to the placing face is determined so that the tension of the film may act in a direction in which the tension presses the flapper against its placing face.
Generally, a gripping part of a flapper is formed with a plane so that it can grip a film in a planar form.
Patent Document 1: JP 2005-104081 A
Patent Document 2: JP 4-230704 A
Patent Document 3: JP 5-11111 A
Patent Document 4: JP 5-11114 A
Patent Document 5: JP 5-288931 A
Patent Document 6: JP 5-288932 A